I'm looking into recievers and I just really need to understand modern sound systems more. I'm sure we have some audiophiles who love to talk about this, so give me some solid, more or less unbiased help. As near as I can tell, these are the options out there:

#1 - Audio stream formats.#2 - Upmixing methods.#3 - Audio stream formats.#4 - Just a certification. Meaningless for the most part. Well, it tells you that the equipment in question doesn't completely suck.

Regarding audio formats, the "current" best stuff is Dolby TrueHD and DTS Master Audio. So if you're shopping for a receiver, the more the merrier. Regarding upmixing, recent receivers have plenty of those. You'll find that for the most part, the receiver market is segregated by: amp power / HDMI ins&outs / number of speakers / upconversion quality / other connectivity and goodies.

There is a fixed amount of intelligence on the planet, and the population keeps growing :(

I had the privilege of listening to the Cambridge Audio Topaz SR10 which is a stereo receiver and it absolutely blew away a mid range Yamaha AV/Receiver. The Yamaha receiver sounded horribly flat in comparison, I guess the audiophile term is muddy. You would expect this of a dedicated stereo receiver but what I am getting at is... don't cheap out when it comes to a good unit.

The newest options are the TrueHD, DTS Master Audio, and Pro Logic II z. Odds are if you find a receiver that supports those three, it will have no problem supporting all the other formats. Now actually getting your receiver to decode TrueHD or DTS Master Audio is a different story.

These audio formats are only available on Blu-Ray or HD DVD, and you must have your player set to bitstream the audio. Not all players are capable of this feature. If your player can't bitstream, the decoding will be done at the player itself. So either the audio gets decoded at the player, or the receiver. The end result will be the same audio information, but if it's decoded at the player and then sent to the receiver, your receiver will not turn on the TrueHD or DTS MA lights. Also, these formats can only be sent via HDMI (1.3a and up I believe). Optical, Digital Coax, RCA, etc. will not be able to transmit the hi-def audio signals.

The various Pro Logic formats basically intelligently upconvert (is that the right word?) a stereo signal to a surround sound signal. The Gamecube and Wii both advertise this, but honestly any signal can be processed thru the Pro Logic formats.

I had the privilege of listening to the Cambridge Audio Topaz SR10 which is a stereo receiver and it absolutely blew away a mid range Yamaha AV/Receiver. The Yamaha receiver sounded horribly flat in comparison, I guess the audiophile term is muddy. You would expect this of a dedicated stereo receiver but what I am getting at is... don't cheap out when it comes to a good unit.

Did you really have an equal comparison when making these observations? Always pay close attention to settings and speaker configurations. The speakers and their placement in the room have the largest single impact of any component. The post-processing effects have the next greatest impact; some effects may sound nice but are not actually faithful to the source, which is often more of a preference issue than an absolute quality issue. Finally, the amplifier construction and the absolute position of the volume control have the third largest impact on perception.

Unfortunately, still another factor that influences audio quality is the cost and appearance of the equipment. Sound perception is so subjective that, just like wine and food tasting, if you believe you're experiencing something superior, you will perceive something superior apart from any objective differences.

You should always be wary when something "sounds so good that it makes the other sound flat".

This can easily be accomplished by DSP effects that are actually distorting the sound. I recall an argument I had before with someone where they insisted that there ought to be a gap in the frequency response between 80Hz and 120Hz (we were setting up a subwoofer) because it sounds better.

I had the privilege of listening to the Cambridge Audio Topaz SR10 which is a stereo receiver and it absolutely blew away a mid range Yamaha AV/Receiver. The Yamaha receiver sounded horribly flat in comparison, I guess the audiophile term is muddy. You would expect this of a dedicated stereo receiver but what I am getting at is... don't cheap out when it comes to a good unit.

Did you really have an equal comparison when making these observations? Always pay close attention to settings and speaker configurations. The speakers and their placement in the room have the largest single impact of any component. The post-processing effects have the next greatest impact; some effects may sound nice but are not actually faithful to the source, which is often more of a preference issue than an absolute quality issue. Finally, the amplifier construction and the absolute position of the volume control have the third largest impact on perception.

Unfortunately, still another factor that influences audio quality is the cost and appearance of the equipment. Sound perception is so subjective that, just like wine and food tasting, if you believe you're experiencing something superior, you will perceive something superior apart from any objective differences.

Ya pretty much as equal as we could get it. This was in a show room where they used the same source, speakers and location. It was an eye opener.

Cambridge Audio is apparently budget to mid tier so it's surprising to hear a tremendous difference. Been ages since I spent a lot of time in high end hifi stores but generally speaking you do get what you pay for (as long as it isn't Monster cable and the like). Separates are still the way to go if you really want nice sound unless somethings changed dramatically in the last 4-5 years.

As other folks said make sure it's not dsp trickery or bizarre treble/bass settings.

I have nothing against humanity that thousands of years of nuclear winter won't take care of.

Back in the day it meant that you had separate components for your CD player, amp/receiver, etc.. These days I guess it could refer to a separate pre-amp/processor and amplifier(s). The opposite is usually "integrated", like when you have speakers with integrated amps and processing, or a cd-player-amp combo.